Perfusion safety valve

ABSTRACT

A perfusion safety valve for use in blood oxygenating systems. The valve includes an elongated, rigid, perforated tube and interiorly disposed therein is a collapsible membrane-like wall which may collapse to cut off the flow of blood through the tube. Exteriorly of the tube is a second membrane-like wall and the space between the two membrane walls is filled with a liquid. When a slight vacuum is pulled against the inner membrane wall, the liquid will pass through the perforations of the tube into the interior of the tube to cause collapse of the interior wall to shut off the flow through the valve to preclude the pumping of air into the arterial system of a patient using the oxygenating system.

Emit/ed States Patent 1 Dewall [54] PERFUSION SAFETY VALVE [76]Inventor: Richard A. Dewall, 247 Northview Rd., Dayton, Ohio 45419 [22]Filed: Aug. 3, 1971 [211 Appl. No.: 168,642

[52] U.S. Cl ..137/565, 23/2585, 128/214 R, 137/525, 251/5 [51] Int. Cl...A61m 5/16 [58] Field of Search...23/258.5; 251/4, 5; 128/214 R,128/214 E, 214 F, 274; 137/494, 511, 525, 525.1, 565; 3/DIG. 3

[56] References Cited UNITED STATES PATENTS 3,513,845 5/1970 Chesnut etal. ..l28/2l4 R 2,756,959 7/1956 Hill ..251/5 2,572,658 10/1951 Perkinsv ..l37/494 X 3,183,908 5/1965 Collins et al.. ..23/258 5 3,204,6319/1965 Fields 23/258 5 2,964,285 12/1960 Bardet ..25l/5 1 Feb. 20, 19732,982,511 5/1961 Connor ..251/5 Primary ExaminerAlan Cohan AssistantExaminer-Gerald A. Michalsky Attorney-Axel A. Hofgren et al.

[57] ABSTRACT A perfusion safety valve for use in blood oxygenatingsystems. The valve includes an elongated, rigid, perforated tube andinteriorly disposed therein is a collapsible membrane-like wall whichmay collapse to cut off the flow of blood through the tube. Exteriorlyof the tube is a second membrane-like wall and the space between the twomembrane walls is filled with a liquid. When a slight vacuum is pulledagainst the inner membrane wall, the liquid will pass through theperforations of the tube into the interior of the tube to cause collapseof the interior wall to shut off the flow through the valve to precludethe pumping of air into the arterial system of a patient using theoxygenating system.

3 Claims, 5 Drawing Figures e 0 XYGEN/l To PA TIE/VT vm v5 K14 PERFUSIONSAFETY VALVE BACKGROUND OF THE INVENTION This invention relates toperfusion safety valves par ticularly suited for use in bloodoxygenating systems.

The continuing progress of medical science has resulted in highlycomplicated surgical procedures becoming relatively commonplace. Oneclass of such procedures involves the use of heart lung machines or thelike wherein blood is removed from the venous system of a patient,oxygenated and returned to the arterial system of the patient.Typically, structures known as oxygenators are employed in suchprocedures and require monitoring by trained personnel to insure thatblood in the oxygenating system will not be exhausted with the resultthat air might be pumped into the patient to cause air embolism, acondition frequently resulting in death. As a safeguardagainstinattentive.- ness of an attendant monitoring the blood level in theoxygenating system, it is desirable to provide means for automaticallycutting off the flow of blood should blood reach a predetermined degreeof exhaustion to preclude the pumping of air into the patient, such as avalve.

SUMMARY OF THE INVENTION It is a principal object of the invention toprovide a new and improved perfusion safety valve for receipt in a bloodoxygenating system that is responsive to exhaustion of blood in anoxygenator or the like to automatically stop the flow of fluid through aline leading to the patient to preclude the pumping of air into thepatients arterial system and the attendant catastrophic results. Moreparticularly, it is an object of the invention to provide such a valvethat is inexpensive to manufacture, is positive in its action withoutrequiring the use of equipment peripheral-to that employed in theoxygenating system to perform its function, and which may be disposed ofafter a single use if desired.

The exemplary embodiment of the invention achieves the foregoing objectsby means of a construction employing an elongated, perforated, rigidtube. About the entire inner periphery of the tube there is provided aflexible, blood compatible membrane, while exteriorly of the tube, agenerally similar membrane is provided. The two membranes are arrangedwith respect to each other and to the tube such that the closed spacebetween the two membranes having a volume at least slightly greater thanthe volume of the interior of the tube results. The close space isfilled with a biologically harmless liquid such as a saline solution.

When employed in an oxygenating system, the typical positivedisplacement pump for the blood line is located downstream of the valve,and the valve is located downstream of an oxygenator or the like.Normally, the head of the blood in the oxygenator will be sufficient tomaintain the inner membrane in substantial abutment with the interiorwall of the tube so that blood may flow therethrough. When the headdecreases to a certain value, the slight vacuum pulled by the pump willresult in atmospheric pressure being applied to the outer membraneforcing the liquid in the closed space through the perforations into thetube to the interface between the interior of the tube and the innermembrane thereby causing the latter to collapse upon itself to terminatethe flow of fluid through the line.

Thus, the construction requires no operating components other than thepositive displacement pump used in the oxygenating system itself andshould the same fail, it will be obvious that there would be no chanceof air embolism by reason of the ceasing of the pumping action. This isin contrast to an arrangement wherein exterior equipment: might beemployed to control the valve position which equipment could fail whilethe pump continued in operation, in which case, the valve would beineffective.

For ease of use, barbed tubular extensions are secured to opposite endsof the tube for connection into typical plastic blood conduit tubingemployed in such systems.

Other objects and advantages will become apparent from the followingspecification taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram illustrating atypical oxygenating system with which the inventive valve is designed tobe employed;

FIG. 2 is a sectional view of a valve made according to the inventionshowing the component parts when the valve is open;

FIG. 3 is a sectional view of the valve in a closed condition;

FIG. 4 is a cross section of the valve in an open condition; and

FIG. 5 is a cross section of the valve in a closed condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT One typical system in which avalve made according to the invention is intended to be used isillustrated in schematic form in FIG. 1 and is seen to include aconventional blood oxygenator 10 adapted to receive venous blood from apatient 12. Downstream of the oxygenator 10, and physically below theoxygenator is a perfusion safety valve, generally designated 14, so thata head of blood is applied thereto. Downstream of the valve 14 is apositive displacement pump 16 which, in turn, provides oxygenated bloodto the arterial system of the patient. As will be seen, the physicallocation of the valve 14 with respect to the oxygenator 10 is of somesignificance insofar as the valve in part responds to the lack ofestablishment of a predetermined head of blood applied thereto. Thisfactor, coupled with the slight vacuum pulled by the positivedisplacement pump 16, will cause the valve 14 to close if the blood inthe oxygenator reservoir 10 becomes exhausted.

Turning now to FIG. 2, an exemplary embodiment of the valve 14 isillustrated in cross section. The valve 14 comprises an elongated, rigidtube 18 which may be formed of polycarbonate, methacrylate or similarplastic. The tube 18 is perforated as at 20 (additional perforations 20may be located along virtually the entire length of the tube 18, ifdesired) and includes internal steps 22 at its ends.

Within the tube 18 is a circumferential membrane film 24 defining ablood impermeable wall. The membrane 24 is sufficiently flexible so thatthe same may collapse upon itself within the interior of the tube to cutoff the flow of fluid therethrough and is formed of any suitable bloodcompatible material such as silicone rubber or a polyvinyl plastic.

Exteriorly of the tube 18 is a second peripheral membrane film 26, alsoformed of any suitable flexible material. The membranes 24 and 26 definea closed space 28 having a volume at least slightly greater than thevolume of the interior of the tube 18 between the ends of the membranes24 and 26 (and in the embodiment illustrated in FIGS. 2 and 3, the endsof the tube 18) and which is adapted to receive biologically harmlessliquid such as a saline solution. If desired, the outer film 26 may beprovided with a suitable sealable port (not shown) for the purpose ofintroducing a liquid into the closed space 28.

The ends of the membrane 26 are sealingly secured to the ends of thetube 18 in any suitable fashion to partially define the closed space 28while the ends of the membrane 24 may be received in the steps 22 of thetube 18. To maintain the same in sealed engagement therewith, anysuitable means such as an adhesive may be employed or, in thealternative, for the two-fold purpose of establishing sealing engagementbetween the membrane 24 and the tube 18 and to facilitate connec tion ofthe latter into blood conduit tubing, tubular extensions 30 havingcomplementary steps 32 may be received in the steps 22 and securedthereto to sealingly hold the ends of the membrane 24 thereagainst. Theextensions 30 include barbed ends 34 for receipt into conventionalplastic tubing employed in the blood line.

In operation, a suitable conduit from the oxygenator will be secured toone of the barbed extensions 30 while the conduit to the pump 16 will besecured to the other barbed extension 30. As long as the head of bloodwithin the oxygenator reservoir exceeds a predetermined level, thepressure of the same will maintain the membrane 24 in the positionillustrated in FIGS. 2 and 4 so that blood may pass through the valve 14to the pump 16 and then to the patient 12. However, should the head ofblood in the reservoir fall below the desired level, the slight vacuumpulled by the pump will result in the atmospheric pressure applied tothe outer membrane 26 collapsing the same driving the saline solutionwithin the closed space 28 through the perforations to force the innermembrane 24 to seal upon itself as illustrated in FIGS. 3 and 5 to haltthe flow of fluid through the line while at least a minimal quantity ofblood remains therein to preclude any possibility of air embolism.

According to one embodiment of the invention, the internal diameter ofthe tube 18 is about three-eighths of an inch while the length of thesurface of the inner membrane 24 that may collapse upon itself will beat least ten times that length so that the capability of sealing uponcollapse is enhanced. For a typical construction, this would require alength on the order of 4 to 6 inches.

From the foregoing, it will be appreciated that a valve made accordingto the invention does not require operating equipment other than thatfound in the oxygenating system itself so that system failure cannot beoccasioned by failure of peripheral equipment. Moreover, the simplicityof construction coupled with positive action results in an inexpensiveconstruction that is completely reliable and one which may be disposedof after a single use.

I claim: 1. A blood oxygenating system including a perfusion safetyvalve comprising an elongated, relatively rigid, perforated tube; meansat each end of said tube for connecting the same into a conduit in whichblood is flowing; a peripheral inner membrane wall formed of a flexiblematerial compatible with blood within said tube; an outer membrane walloutside of said tube; said inner and outer membrane walls defining aclosed space; and a liquid within said closed space; whereby when bloodis flowing through said tube, said inner membrane wall will be insubstantial abutment with the internal surface of said tube while whenblood ceases to flow to said tube, a slight vacuum in the blood linewill cause the liquid in said closed space to flow through theperforations in said tube to cause said inner membrane wall to collapseupon itself to seal off the blood line, a blood oxygenator adapted toreceive blood from a patient for oxygenating the same; meansestablishing a blood flow path from said oxygenator to one of saidconnecting means; a blood pump; means establishing a blood flow pathfrom the other of said connecting means to said blood pump, said bloodpump being adapted to conduct oxygenated blood to the patient andfurther being a positive displacement pump whereby a slight vacuum maybe pulled upstream of the same so that the absence of blood flowing fromsaid oxygenator to said valve will result in said valve closing topreclude the pumping of air into the arterial system of the patient.

2. The blood oxygenating system of claim 1 wherein said inner membranewall has a length equal to about at least ten times the cross sectionaldimension of "said tube; said closed space has a volume at leastslightly greater than the volume of the interior of said tube along thelength of the inner membrane wall; and the liquid in said closed spaceis a biologically harmless liquid.

3. A blood oxygenating system according to claim 2 wherein saidconnecting means comprise barbed, tubular extensions on both ends ofsaid tube.

1. A blood oxygenating system including a perfusion safety valvecomprising an elongated, relatively rigid, perforated tube; means ateach end of said tube for connecting the same into a conduit in whichblood is flowing; a peripheral inner membrane wall formed of a flexiblematerial compatible with blood within said tube; an outer membrane walloutside of said tube; said inner and outer membrane walls defining aclosed space; and a liquid within said closed space; whereby when bloodis flowing through said tube, said inner membrane wall will be insubstantial abutment with the internal surface of said tube while whenblood ceases to flow to said tube, a slight vacuum in the blood linewill cause the liquid in said closed space to flow through theperforations in said tube to cause said inner membrane wall to collapseupon itself to seal off the blood line, a blood oxygenator adapted toreceive blood from a patient for oxygenating the same; meansEstablishing a blood flow path from said oxygenator to one of saidconnecting means; a blood pump; means establishing a blood flow pathfrom the other of said connecting means to said blood pump, said bloodpump being adapted to conduct oxygenated blood to the patient andfurther being a positive displacement pump whereby a slight vacuum maybe pulled upstream of the same so that the absence of blood flowing fromsaid oxygenator to said valve will result in said valve closing topreclude the pumping of air into the arterial system of the patient. 1.A blood oxygenating system including a perfusion safety valve comprisingan elongated, relatively rigid, perforated tube; means at each end ofsaid tube for connecting the same into a conduit in which blood isflowing; a peripheral inner membrane wall formed of a flexible materialcompatible with blood within said tube; an outer membrane wall outsideof said tube; said inner and outer membrane walls defining a closedspace; and a liquid within said closed space; whereby when blood isflowing through said tube, said inner membrane wall will be insubstantial abutment with the internal surface of said tube while whenblood ceases to flow to said tube, a slight vacuum in the blood linewill cause the liquid in said closed space to flow through theperforations in said tube to cause said inner membrane wall to collapseupon itself to seal off the blood line, a blood oxygenator adapted toreceive blood from a patient for oxygenating the same; meansEstablishing a blood flow path from said oxygenator to one of saidconnecting means; a blood pump; means establishing a blood flow pathfrom the other of said connecting means to said blood pump, said bloodpump being adapted to conduct oxygenated blood to the patient andfurther being a positive displacement pump whereby a slight vacuum maybe pulled upstream of the same so that the absence of blood flowing fromsaid oxygenator to said valve will result in said valve closing topreclude the pumping of air into the arterial system of the patient. 2.The blood oxygenating system of claim 1 wherein said inner membrane wallhas a length equal to about at least ten times the cross sectionaldimension of said tube; said closed space has a volume at least slightlygreater than the volume of the interior of said tube along the length ofthe inner membrane wall; and the liquid in said closed space is abiologically harmless liquid.